_____________________________________________________ krmanjunathsac.isro.gov.in
REMOTE SENSING BASED METHANE EMISSION INVENTORY VIS-A-VIS RICE CULTURAL TYPES OF SOUTH ASIA.
K R Manjunath
a
, Revati More
a
, Prakash Chauhan
a
, Anjana Vyas
c
, Sushma Panigrahy
b
and J.S. Parihar
b a
Space Applications Centre, Indian Space Research Organisation, Ahmedabad, India – krmanjunathsac.isro.gov.in
b
Formerly with Space Applications Centre, Indian Space Research Organisation, Ahmedabad,India
c
CEPT University, Ahmedabad, India
Commission VI, WG VI4 KEY WORDS
:
Methane, IPCC, Rice cultural types, South-Asia, Remote Sensing, GIS ABSTRACT
Rice cultivation has been recognized as one of the major anthropogenic source for methane CH4 emissions which is a microbial mediated anaerobic activity, mainly favoured by the flooded conditions in the rice fields. Information available on CH4 emission is
limited, especially in a spatial domain, mainly because of the complexity involved in generating such data. The current approach demonstrates the use of secondary data sources available on the methane emission scaling factors, coupled with the information
derived on rice cultural types and crop calendar. Methane emission from each type of rice field was firstly calculated by multiplying the emission factor by the corresponding cultivation area and length of cropping period. The values were then extrapolated over each
country with respect to the rice area and crop duration for under each cultural type. The rice cultural type wise methane emission value for South Asia was derived by summation of individual emission values for the respective cultural type within each country.
The total methane emission derived for South Asia region is 4.7817 Tgyr. The mean methane emission estimates derived for each country are viz. India 3.3860 Tgyr, Bangladesh 0.9136 Tgyr, Pakistan 0.2675 Tgyr, Sri Lanka 0.1073 Tgyr and Nepal
0.1074 Tgyr. The derived methane emission estimates could be used to study the regional variations within the country and also to adopt the mitigation strategies to combat the high methane emission values within specific cultural type by means of altering the
farming practise or water regime.
1. INTRODUCTION Methane CH
4
emission from various sources is an important matter of concern because of its relatively fast increase and its
per molecule, 60 times more effectivity than CO
2
in causing global warming IPCC, 2001. Rice cultivation has been
recognized as one of the major anthropogenic source for CH
4
emissions Denier Van Der Gon, 2000; Li et al, 2002. Methane emission for the rice fields is a microbial mediated anaerobic
activity, mainly favoured by the flooded conditions in the fields. Increase in rice production is suspected to meet the food
demand for rising population which will lead to increase in methane emissions by 36 percent from rice fields in South and
South-East Asia US-EPA,2006. It has been reported that rice fields contribute about 10–15 to global CH
4
emissions Prather Ehhalt, 2001,with an estimated annual emission of
50–100 Tg of methane Reiner and Milkha 2000 and 33 to 40 TgyrYan et al, 2009. Flooded rice fields are the third largest
source of agricultural emissions and contribute about 10 - 30 of the global methane arising from anaerobic decomposition of
organic matter Wahlen et al, 1989. Various biotic and abiotic factors viz. temperature, humidity,
soil organic matter, manure amendments, temperature, water status, soil characteristics, moisture content and microbial
activity, availability of methanogenic substrate generated from organic residues, plant-borne material available during the
cropping season affect the rate of methane emission from rice fields Cicerone et al, 1988, Ehhalt,1974,Wahlen et al,1989.
Thus methane assessment with respect to rice cultural types is essential as it is influenced by the field conditions. The methane
emission assessment requires the information on rice growing areas. In present paper we demonstrate the use of geospatial
rice datasets and adaption of cultural type specific emission co- efficient to derive country-level methane emission inventory for
South Asian countries. Owing to its role in food security, rice will play a major role in
the methane emission and apparently in increasing trend of atmospheric methane concentration. Thus it is necessary to
estimate the methane emission for rice fields in context to a strong inter-relationship between agriculture and climate
change. Information available on CH
4
emission is limited, especially in a spatial domain, mainly because of the
complexity involved in generating such data. Also the ground sampling over the large extent of study area is not feasible in
most of the countries. Considering significance of methane emission and current scenario, the present work aims to derive
the spatial pattern of methane emission for major rice producing countries of South Asia by integrating a remote
sensing and GIS approach. 2. METHODOLOGY
2.1 Study area: The study constitutes of major rice growing countries of South Asia viz. India, Bangladesh, Nepal, Pakistan
and Sri Lanka as these countries from a rice bowl of Asia. 2.2 Data used: The spatial data for cultural type-wise rice area
and rice crop calendar for the study region derived using a SPOT VGT NDVI data and GIS data was used as a base map
for developing a methane emission coefficients.
ISPRS Technical Commission VIII Symposium, 09 – 12 December 2014, Hyderabad, India
This contribution has been peer-reviewed. doi:10.5194isprsarchives-XL-8-821-2014
821
The detailed methane emission assessment with respect to the rice cultural types was carried out over India. The season-wise
and state-wise sampling for in-situ measurements was conducted for total 471 sampling units over India by Manjunath
et al, 2008. The total methane emission from the rice lands was calculated by multiplying the rice area within a stratum by
corresponding emission values and range of emissions minimum and maximum by using a Standard emission factors
SIFs within a category, as suggested by the approach used earlier by Manjunath et al, 2008.
2.3 Analysis approach: The methane emission from rice fields is directly proportional to area under the rice cultural type and
total crop duration. Earlier allocation of areas to rice cultural types were allocated on the basis statistical data for harvested
rice area or country specific reports to calculate the methane emission values Yan et al,2009; Gupta et al,2008; IPCC,
1996.The statistical data has its own limitations as the timely procurement of data involves a labour n time cost. Application
of the remote sensing derived information on rice croplands will provide a valuable input for CH
4
emission studies. The current approach demonstrates the use of secondary data
sources available on the methane emission scaling factors, coupled with the information derived on rice cultural types and
crop calendar using a remote sensing and GIS data. The rice area within a country was stratified into the IPCC compliance
rice cultural types with potential environment for methane emission viz. wet continuous irrigated, intermittent flooded,
flood prone, drought prone, deep water. The information on the total duration of rice crop was derived from the remote sensing
based rice crop calendar Figure 1. Table 1. Standard CH
4
emission factors kghaday with respect to IPCC specified rice cultural types Calculated from
Indian methane emission inventory, Manjunath et al, 2006 Rice Cultural
Type IPCC
specified Total CH
4
emission CH
4
kgha Total crop
duration No. of
Days Seasonal
Integrated Flux
SIF CH
4
kghaday Irrigated
Continuous Wet Season
75.10 120
0.63 Irrigated
Intermittent 55.00
120 0.46
Flood Prone 137.8
125 1.10 Drought
Prone 62.40
120 0.52 Deep Water
343.81 130 2.64
Irrigated Continuous
Dry season 78.34
120 0.65
Upland - -
- Earlier a detailed methane emission assessment was carried out
over Indian region, which involved the close chamber sampling techniques for the CH
4
emission measurements Manjunath et al,2006. In present study the average methane emission
coefficient derived over the India and standard emission factors as suggested by IPCC
Intergovernmental Panel on Climate Change were used for the methane emission assessment.
The methane emission assessment for different countries is carried out by extrapolating the emission values from Indian
rice paddies. The methane emission rates for each country were estimated based on the rice area derived using remote sensing
data and the extrapolating the methane emission factors of Indian region. The quantification of the seasonal integrated flux
SIF kghaday for CH4 emission factor was deduced from the Indian CH4 emission factors Table 1.
M ethane emission from
each type of rice field was firstly calculated by multiplying the emission factor by the corresponding cultivation area and
length of cropping period Equation 1. TCH
4
=SIF AD
1 where TCH
4
is the annual total CH
4
emission from the rice fields, SIF
is the seasonal integrated fluxemission factor, A is the rice area in ha, D is the total crop duration of the rice
cultural type in a cropping season. The values were then extrapolated over each country with respect to the rice area and
crop duration for under each cultural type. The remote sensing derived crop duration was used for calculating D. Present
approach envisages the use of remote sensing and GIS techniquesderived input to assignestimate the methane
emission values over a large study area base on major factor of rice cultural type and duration.
Figure 1. Schematic methodology for the methane emission assessment
3. RESULTS AND DISCUSSIONS This methodological approach demonstrates the gross CH
